Many of us have been in this situation: after a late Friday night out, you want to sleep in on a lazy Saturday morning only to have your industrious neighbor power up his ancient, noisy, powered lawnmower at the crack of dawn. So much for that plan.
However, the folks at Briggs & Stratton are hard at work developing products to help you sleep in more soundly on Saturday mornings. The company’s newly renovated Noise, Vibration and Harshness (NVH) laboratory, located in Wauwatosa, WI features two anechoic chambers outfitted with sound-absorbing acoustic wedges from Eckel Noise Control Technologies (Ayer, MA). These chambers are designed—among other things—to analyze and tailor the noise produced by small engines used in a range of lawn, garden and light construction equipment, including lawn mowers, standby generators, power washers, snow blowers and air compressors.
The renovation was performed by ACS, Inc. (Middleton, WI). The two anechoic chambers were designed and build by ACS and Eckel, which was also tasked with supplying the acoustic treatment for the test chambers. Installation of the acoustic wedges was performed by Viking Enterprises, Inc. (Waterford, CT)
Noise reduction has become a very important aspect of outdoor powered equipment design as consumers have demanded it and both the US and the EU have developed noise emission standards.
The smaller chamber, known as the 2M chamber because it accommodates a 2-meter hemispherical array of microphones for sound testing, has an interior dimension of 21 ft. 1½ in. wide, 26 ft. 4½ in. long and 10 ft. 9 in. high. This chamber is used for engine product development and testing of smaller finished products like lawn mowers, snow blowers and pressure washers. A 30 HP dynamometer is contained in an isolated, subfloor enclosure. The setup allows engineers to measure and control engine vibration and to design quieter engines with a pleasing tone and pitch. An overhead monorail crane is used to move equipment into place.
The larger chamber, called the 4M chamber, has a 4-meter hemispherical microphone array and has an interior dimension of 32 ft. 8¾ in. wide, 33 ft. ¾ in. long and 17 ft. 8 in. high. This chamber is used to analyze larger equipment like lawn and garden tractors and large home standby generators. Below the floor is an isolated 40 HP dynamometer. This chamber is also used for certification testing to ensure that products comply with domestic and international noise regulations. The chamber features a large overhead bridge crane to move equipment. Both chambers were designed with ventilation systems that provide 100 percent air change per minute to accommodate engine exhaust while maintaining a constant chamber temperature.
Having two chambers gives Briggs & Stratton increased productivity and unparalleled flexibility. The company makes engines not only for its own branded products, but also for other OEMs such as MTD and John Deere. Briggs & Stratton offers the use of the chambers to its OEMs for the testing of their finished products. No other engine manufacturer has this capability.
Eckel outfitted both chambers with its standard, perforated-metal sound absorbing wedges designed with a 100Hz cutoff (per ISO 3745 standard), meaning that 99.0 percent of the sound energy generated above that frequency is absorbed by the panels. A key challenge, according to Eckel’s Jeff Morse, VP of Engineering, was to maintain the acoustic integrity of the chamber given the stringent HVAC system requirements.
Briggs & Stratton found that working with ACS and Eckel to build the chambers was a most gratifying experience. “The ACS and Eckel teams were excellent. I can’t say enough about how they worked to get us exactly what we wanted,” said Brett Birschbach, Briggs & Stratton’s NVH Engineering Manager.
According to Randy Rozema, Director, Applications Engineering of ACS, “Eckel’s vast experience helped to integrate the functional requirements of Briggs & Stratton’s testing into a multipurpose test space set to support testing needs well into the future. The finished installation was something Eckel and ACS proudly turned over to Briggs & Stratton at the end of the project”
Adds Eckel’s Jeff Morse, “We were pleased to work with Briggs & Stratton and ACS and apply our expertise in the automotive industry to the small engine segment.”
Since the chambers became operational, they’ve been in use almost non-stop. The only noise coming from them is the hum of activity from equipment moving in and out.
Filed Under: Test + measurement • test equipment